Control your 3020/3040/6040 or similar with GRBL, without modifying your control box. This version works with JP-382A stepper driver board commonly found in these CNC machines.
Does this even work? Your schematic doesn't have a crystal for the CH340G, and datasheet says its required. And I'm guessing you just use GRBL firmware?
question, where can I get the firmware for atmega?